The primary purpose of toothbrushes is to remove plaque and debris from tooth surfaces, both along their outer surfaces and in the interproximal areas between the teeth. As disclosed in U.S. Pat. No. 5,511,275, to Volpenhein, the bristle tufts of a toothbrush must be sufficiently stiff to generate enough force to remove plaque and debris, especially in the interproximal areas. Stiffness, as defined by Volpenhein, not only relates to the stiffness characteristics of bristles, but also to how the bristles are arranged in tufts, i.e. a buttressing effect.
U.S. Pat. No. 5,628,082, to Moskovich discloses a combination of conventional bristle tufts, i.e. substantially cylindrical in form and bristle bars, i.e. enlarged tufts of bristles arranged in elongated geometric forms with substantially rectangular cross-sections. The particular bristle bars disclosed in Moskovich have rectangular or U-shaped foot-prints and are combined with the bristle tufts in a generally transverse alignment to the longitudinal axis of the brush head. In the most preferred embodiment, the bristle bars are shorter than the bristle tufts, allowing the bristle tufts to engage the interproximal spaces between the teeth and the bristle bars to squeegee the debris from the teeth surface. Further, Moskovich discloses "gumline" tufts located about the periphery of the toothbrush head which are angled outward. Moskovich does not disclose the use of such gumline bristle tufts in combination with bristle bars oriented substantially parallel to the longitudinal axis of the toothbrush.
There is a continuing need in the art for new combinations and arrangements of bristle tufts to provide improved stiffness to enhanced plaque and debris removal, especially within interproximal spaces.